How can I bypass expensive transmission repairs

Hello I was on here last Saturday or sunday about my 2004
chevy venture.  I had stated that I felt a mild jerk when
shifting into gears especially 2nd gear with a hard shift
going into 3rd.  Decided to take it to continental
transmission to have it diagnosed.  Although no lights are
on at alllll in the vehicle with 105,500 miles on it.  I was told
code p1811 massive adapt and long shift is the problem
with the transmission.   He stated he's suprised the engine
light isn't on.   I was told quite a bit of money to have fix it
by continental transmission.  Help me any better solutions
to this problem.   Van rides great other than when it
experience those mild and hard shifts in 2nd and 3rd gear,
and I just bought it just a little over a month ago now